This is a very good question. There have been inside cheats at poker rooms and of course there is Ultimate Bet failing when Online poker was decimated with the passing of the port Authority act in 2006. UB did not have enough money to cover withdrawals because deposits were not fenced and the money had been used by owners and sponsored players for other things. But UB had no upside to doing this, just put them out of business.
We have all seen the many allegations of online poker being rigged, and these are made as far as I can see by people just venting because they are going broke, or simply do not understand odds. It is relatively easy to figure out if online poker is rigged. It is just a matter of documenting enough hands to pickup variance, as Chris said in his reply. This is how players picked up on the inside tournament heist mentioned earlier in this reply.
I just want to make the simple argument that using a "cooler" to make more action is not really a viable way to cheat players. You do not risk a multi million dollar business cheating players in such a transparent way. You will loose your business when you are soon discovered. In B&M poker this rant about the deck being rigged has been heard as long as there has been a game, in online poker this rant is written, but it is the same looser rant. Cheating players in this way is not likely to happen.
You would need to cheat in such a way that it is not particularly discoverable, were you have culpable deniability. There is such a way, it is common and the public card rooms both online and B&M enjoy profits from it. It is not a cheat that rigs the site, it is simply allowing by policy and indifference to allow cheats to play.
There is a paradox in poker. The house makes money by running the games, not by policing the games. To police a game, the business needs to spend more money on security. Policing the game results in a lose of paying customers, as one bust cheats.
The problem is that almost all players cheat. I could not convince most of you that you cheat, but if you have ever checked it down with another player, like a friend, your husband or wife, you have participated in collusion. Most cheating is collusion and poker rooms claim that collusion is hard to detect.
But what is really happening is that management is constantly trying to set the bar between security and not loosing customers that pay for the service.
In the movie rounder's Matt and the Worm take a trip to Atlantic City, in the voice over Matt talks about the rounder's sitting around waiting for the live one. He says that they do not really play hard against each other, and that it is not really cheating.
But it is a sort of collusion when the implied agreement between them is that we fleece the live ones not each other. This kind of scene is common in a casino. You could be a real stickler of a card room shift manger and logically decide these regular player are colluding and say hey go play someplace else. But nobody does, not because it is not colluding, because you would have no business for long.
Consider this scenario, you are the CEO ofbestpokeronline.com. You have been lucky and one of your players has won the WSOP and your online poker room is now making billions. You take game security very seriously. You spend tens of millions on developing software that detects cheating and bots. You talk about your great security all over your website. One day as your sitting in your office on high, smoking Cuban cigars, drinking Dom Peron with the Swedish bikini team on a big pile of money, your chief of security calls and says great news boss, we have developed software that detects bot play 100%. You lite another Cuban up, dismiss the bikini team, this is great news. Your COS elaborates on the software, saying there is one tiny downside, 28% of our revenue comes from bots.
On all levels, people in the poker industry make decisions that compromise game security in favor of the bottom line. This is a rigged game by any standard. To answer the question, yes the game is rigged, because the upside is it helps the bottom line and may be necessary to even stay in business.